Abstract B069: Double-stranded RNA derived from tandem repeat sequences induces mesenchymal transition in pancreatic cancer cells by regulating alternative splicing

Abstract

Abstract Human satellite II (HSATII) composed of tandem repeats in pericentromeric regions in the human genome is aberrantly transcribed in epithelial cancers, particularly pancreatic cancer. Dysregulation of the repetitive elements in cancer tissues can facilitate incidental double-stranded RNA formation. However, it remains controversial whether double-stranded RNAs play tumor-promoting or tumor-suppressing roles during cancer progression. Therefore, we focused on the formation of double-stranded HSATII (dsHSATII) RNA and explored its molecular functions. The overexpression of dsHSATII RNA promoted mesenchymal-like morphological changes and enhanced the invasiveness of pancreatic cancer cells. We identified an RNA-binding protein, STRBP, which preferentially binds to dsHSATII RNA rather than single-stranded HSATII RNA. Depletion of STRBP induced the mesenchymal transition and enhanced the invasiveness. Conversely, the epithelial–mesenchymal transition (EMT) of dsHSATII-expressing cells was rescued by STRBP overexpression. Mechanistically, STRBP is involved in the alternative splicing of genes associated with the EMT events, which was interfered by the overexpression of dsHSATII RNA. Finally, we confirmed that isoform switching of CLSTN1, one of the target genes of STRBP-associated alternative splicing, induced EMT-like morphological changes. These findings reveal a novel cell-autonomous function of dsHSATII RNA in enhancing malignant potential, providing a better understanding of the biological significance of aberrant expression of satellite arrays in malignant tumors. Citation Format: Takahiro Kishikawa, Takuma Iwata, Motoyuki Otsuka, Mitsuhiro Fujishiro. Double-stranded RNA derived from tandem repeat sequences induces mesenchymal transition in pancreatic cancer cells by regulating alternative splicing [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B069.